15-816 Modal Logic
Lecture 17: Tethered Semantics

In this lecture we present a new form of semantics which
combines multiple worlds with multiple judgments at these
worlds. We find that this so-called tethered semantics
has local actions, and that its sequent calculus is in bijective
correspondence with the sequent calculus JS4 for validity and
possibility. Because antecedents are persistent and just
become unusable instead of being erase, the tethered semantics
is well-suited for implementation of JS4 in a logical framework.